Electrode catheter

ABSTRACT

The objective is to provide a catheter that can realize a desired curved shape by preventing the curving axis of the catheter distal part from twisting, and preventing the catheter from kinking and decreased pushability. Disclosed is a catheter ( 1 ) having a shaft ( 2 ); at least one wire ( 30 ); a coil ( 60 ); a leaf spring ( 40 ) extending in the longitudinal direction and having a first connection part where its proximal part is fixed to a distal end part of the coil ( 60 ); and a cover tube ( 50 ) that is disposed outside the coil ( 60 ) and has a first fixed part ( 51 ) where it is fixed to the shaft ( 2 ) at a position proximal to the distal end of the coil ( 60 ) in the longitudinal direction.

TECHNICAL FIELD

The present invention relates to a catheter with a bendable distal part.

BACKGROUND ART

Electrode catheters with multiple electrodes on the distal part are usedto measure or pace potentials in the heart. Some such catheters withelectrodes have a distal part that is bendable by operating a handle sothat the distal part of the catheter can be easily placed at a desiredsite in the heart. Such catheters generally allow the distal part of thecatheter to be curved by pulling a pull wire fixed to the inside of thedistal end part of the catheter.

In order to deliver the distal part of the catheter to the optimal siteaccording to the size of the heart and purposes, it is required for thedistal part of the catheter to be curved freely in the desired directionby wire manipulation. In addition, in order to prevent the distal partof the catheter from damaging the lumen wall of the living body ortraveling in an undesired direction, it is necessary to prevent orreduce twisting or bending (kinking) of the distal part of the catheterwhen it is curved. For this reason, various forms of fixing the proximalside of the leaf spring for curving have been proposed.

As such catheters, a catheter is disclosed in which the distal ends ofan operating wire and a leaf spring, which is a curving member, arefixed to the distal end of a catheter tube, and the proximal end of thecurving member is connected to a tube disposed in the lumen of thecatheter tube.

The catheters disclosed in Patent documents 1 and 2 have a configurationin which operating wires are disposed in tubes for the operating wires,a leaf spring is disposed in a catheter tube, and the proximal end ofthe leaf spring is fixed to a coil tube. In Patent document 2, the tubesfor operating wires are fixed to the surface of the leaf spring and thelike via an adhesive layer. In the catheter disclosed in Patent document3, a leaf spring is fixed to a coil tube via a coil stopper. In thecatheter disclosed in Patent document 4, an operating wire and a leafspring are disposed in a distal tube, and the proximal end of the leafspring is fixed to a proximal tube. In addition, a protection tube isdisposed outside the proximal tube. It is disclosed that the proximalend of the distal tube is located distal to the distal end part of theprotection tube.

RELATED ART DOCUMENT Patent Document

-   Patent document 1: JP 2006-61350 A-   Patent document 2: JP 2012-200445 A-   Patent document 3: JP 2014-64614 A-   Patent document 4: WO2019/156059

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in conventional catheters, when a coil connected to theproximal end part of the leaf spring is provided to ensure the stiffnessof the base end, the coil is compressed by pulling of the wire, and thecoil is deformed to spread in the radial direction, causing theconnection between the coil and the leaf spring to rotate, whichsometimes causes the curving axis of the leaf spring to twist. In orderto prevent this, the connection part can be fixed to the catheter tube.However, the fixed part becomes hard, resulting in a stiffness step witha sudden change in hardness. This may cause a kink where the catheterbreaks when the catheter is bent, or a decrease in pushability where theforce of wire manipulation is difficult to be transmitted to the tip ofthe wire. In addition, when a conductive wire is placed in the fixedpart, the conductive wire is also fixed, and the conductive wire mayhinder the catheter from bending, adversely affecting the shape of thebend.

The present invention has been made in view of the above circumstances,and its objective is to provide a catheter that can realize a desiredcurved shape by preventing the curving axis of the distal end part ofthe catheter from twisting, while preventing the catheter from kinkingand decreased pushability.

Means for Solving the Problems

A catheter that can solve the above problems has a shaft having a distalend, a proximal end, and a lumen extending in a longitudinal direction;at least one wire having a distal end and a proximal end, the proximalend being disposed at a proximal end part of the shaft, and a distal endpart of the wire being fixed to a distal end part of the shaft; a coilhaving a distal end, a proximal end, and a lumen in which the wire isdisposed and extending in the longitudinal direction in the lumen of theshaft; a leaf spring having a distal end and a proximal end andextending in the longitudinal direction in the lumen of the shaft; and acover tube having a distal end, a proximal end, and a lumen extending inthe longitudinal direction in the lumen of the shaft, wherein the leafspring has a first connection part where a proximal end part of the leafspring is fixed to a distal end part of the coil, and a secondconnection part where a distal end part of the leaf spring is fixed to adistal end part of the shaft; the wire, the leaf spring, and the firstconnection part are disposed in the lumen of the cover tube; the covertube has a first fixed part where the cover tube is fixed to the shaftat a position proximal to the distal end of the coil in the longitudinaldirection; and the cover tube is disposed outside the coil.

Preferably, a part of an inner surface of the cover tube is in contactwith the outside of the coil.

Preferably, a length from a distal end of the first fixed part to thedistal end of the coil is 2 times a length of the leaf spring or shorterin the longitudinal direction.

Preferably, a length from a distal end of the first fixed part to thedistal end of the coil is ⅓ a length of the leaf spring or longer in thelongitudinal direction.

Preferably, the first fixed part is located proximal to the firstconnection part.

Preferably, the cover tube is not fixed to the shaft in the section froma distal end of the first fixed part to the distal end of the coil inthe longitudinal direction.

Preferably, at the first fixed part where the shaft and the cover tubeare fixed, the shaft, the cover tube, and the coil are fixed.

Preferably, the catheter further has a second fixed part where the shaftand the coil are fixed at a position proximal to the first fixed part inthe longitudinal direction.

Preferably, a longitudinal length of the cover tube is longer than alongitudinal length of the leaf spring.

Preferably, the cover tube extends to the second connection part, andthe cover tube covers the wire and the leaf spring so that the wire andthe leaf spring are not exposed in the lumen of the shaft.

Effects of the Invention

The present invention can prevent the curving axis of a bendable distalend part of a catheter from twisting while preventing kinking anddecrease in pushability. This allows a desired curved shape of thedistal end part of the catheter to be achieved by wire manipulation,resulting in providing a catheter that can easily deliver the distal endpart of the catheter to a desired location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a catheter according to one embodiment of thepresent invention.

FIG. 2 is a cross-sectional view of a distal part of the catheter shownin FIG. 1 in the longitudinal direction (partially, a plan view).

FIG. 3 is a cross-sectional view of the catheter distal part shown inFIG. 2 .

FIG. 4 is a IV-IV cross-sectional view of the catheter distal part shownin FIG. 2 .

FIG. 5 is another example of the IV-IV cross-sectional view of thecatheter distal part shown in FIG. 2 .

FIG. 6 is a VI-VI cross-sectional view of the catheter distal part shownin FIG. 2

FIG. 7 is a VII-VII cross-sectional view of the catheter distal partshown in FIG. 2 .

FIG. 8 is a cross-sectional view of a distal part of a catheteraccording to another embodiment of the present invention in thelongitudinal direction (partially, a plan view).

FIG. 9 is a cross-sectional view of a distal part of a catheteraccording to still another embodiment of the present invention in thelongitudinal direction (partially, a plan view).

FIG. 10 is a cross-sectional view of a distal part of a catheteraccording to still another embodiment of the present invention in thelongitudinal direction (partially, a plan view).

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on thefollowing embodiments. The present invention is, however, not limited bythe following embodiments and can be altered in design within a scope incompliance with the intent described above and below, and all thechanges are to be encompassed within a technical scope of the presentinvention. Note that, in each drawing, hatching, reference signs forcomponents, and the like may be omitted for convenience of description,and in such a case, the specification and other drawings are to bereferred to. Furthermore, since the dimensions of the various componentsin the drawings are provided for the purpose of facilitating theunderstanding of the feature of the present invention, the dimensionsmay differ from the actual dimensions in some cases.

The catheter of the present invention has a shaft having a distal end, aproximal end, and a lumen extending in a longitudinal direction; atleast one wire having a distal end and a proximal end, the proximal endbeing disposed at a proximal end part of the shaft, and a distal endpart of the wire being fixed to a distal end part of the shaft; a coilhaving a distal end, a proximal end, and a lumen in which the wire isdisposed and extending in the longitudinal direction in the lumen of theshaft; a leaf spring having a distal end and a proximal end andextending in the longitudinal direction in the lumen of the shaft; and acover tube having a distal end, a proximal end, and a lumen extending inthe longitudinal direction in the lumen of the shaft, wherein the leafspring has a first connection part where a proximal end part of the leafspring is fixed to a distal end part of the coil, and a secondconnection part where a distal end part of the leaf spring is fixed to adistal end part of the shaft; the wire, the leaf spring, and the firstconnection part are disposed in the lumen of the cover tube; the covertube has a first fixed part where the cover tube is fixed to the shaftat a position proximal to the distal end of the coil in the longitudinaldirection; and the cover tube is disposed outside the coil.

With the above configuration, the catheter of the present invention canbend the catheter distal part in the section distal to the distal end ofthe coil by bending the leaf spring connected to the distal end part ofthe shaft with pulling the wire while ensuring the stiffness of the baseend of the shaft end part by the coil. The catheter of the presentinvention with the above configuration can prevent the curving axis ofthe catheter end part from twisting, because even if the coil in whichthe wire is placed in the lumen is compressed by pulling the wire, thecover tube disposed outside the coil makes the outer diameter of thecoil unlikely to deform, such as spreading. In addition, because thecover tube has a first fixed part fixed to the shaft apart from thedistal end of the coil, a stiffness step with a sudden change inhardness at the distal end of the coil can be mitigated, and kinking ofthe catheter and decrease in pushability can be prevented. Furthermore,because the cover tube that is placed outside the coil is fixed to theshaft, it can be made unlikely for the coil to be twisted or otherwisedeformed due to pulling of the wire. Accordingly, the catheter of thepresent invention can easily deliver the catheter distal part to adesired location in a blood vessel or the heart, and also prevent thecatheter distal part from damaging the lumen wall of the living body ortraveling in an undesired direction.

Note that the fixation of the coil, cover tube, and shaft in the presentinvention means that they are fixed by some fixing means, such asadhesion by glue, welding by resin, brazing by solder, etc., and merelycontacting or overlapping firmly are not included in the fixation. Forexample, the cover tube may be provided by heat-shrinking resin on theoutside of the coil, in which case the cover tube may adhere to theoutside of the coil; however, such a condition is not considered as thecover tube and the coil being fixed. Furthermore, if the shaft isprovided on the outer side by heat-shrinking, etc., the coil, the covertube, and the shaft may adhere to each other, and the coil and the shaftmay indirectly adhere. However, such a condition is not considered asthe coil and the shaft being fixed. Moreover, at the section where thecover tube is not placed in the longitudinal direction, the shaft may beprovided in close contact with the outside of the coil. However, such acondition is not considered as the coil and the shaft being fixed.

Hereinafter, a catheter according to embodiments of the presentinvention will be described referring to FIG. 1 to FIG. 10 . FIG. 1 is aplan view of a catheter according to one embodiment of the presentinvention, and the dotted lines represent the appearance when the distalpart of the catheter is curved on one side of the leaf spring in theradial direction of the shaft. FIG. 2 is a cross-sectional view of thedistal part in the longitudinal direction when the catheter shown inFIG. 1 is not curved. In FIG. 2 , the coil is shown as a plan view. FIG.3 is a cross-sectional view of the catheter distal part shown in FIG. 2. FIG. 4 is a IV-IV cross-sectional view of the catheter distal partshown in FIG. 2 , and FIG. 5 is another example of the IV-IVcross-sectional view of the catheter distal part shown in FIG. 2 . FIG.6 is a VI-VI cross-sectional view of the catheter distal part shown inFIG. 2 , and FIG. 7 is a VII-VII cross-sectional view of the catheterdistal part shown in FIG. 2 . FIG. 8 to FIG. 10 are cross-sectionalviews of the catheter distal part according to different embodiments ofthe present invention in the longitudinal direction when the catheter isnot curved, and in FIG. 8 to FIG. 10 , the coil is shown as a plan view.

In the present invention, a proximal side refers to the user's hand inthe direction of shaft extension, and a distal side refers to theopposite side of the proximal side, i.e., the side of the person to betreated. The direction of shaft extension is referred to as alongitudinal direction d_(L). The radial direction perpendicular to thedirection of shaft extension is referred to as a radial direction d_(R).In FIG. 1 , FIG. 2 , and FIG. 8 to FIG. 10 , the lower side of thefigure is the proximal side and the upper side of the figure is thedistal side.

As shown in FIG. 1 , a catheter 1 has a distal end, a proximal end, anda shaft 2 having a lumen extending in the longitudinal direction d_(L).A tip part 20 is preferably disposed at the distal end of the shaft 2,and a handle 7 is preferably disposed at a proximal end part of theshaft 2.

The distal end of the shaft 2 is inserted into the body, and deliveredto a treatment site. For this reason, preferably, it is flexible, andmetals or resins can be used as the material. Since it is inserted intothe body, it is preferable to use biocompatible materials. On thesurface of the shaft 2, devices for treatment, such as electrodes andsensors, can be placed. By providing electrodes on the surface of theshaft 2, it can be used as an electrode catheter to measure cardiacpotential or an ablation catheter to cauterize tissue.

Internal structures for curving the catheter 1, or devices and theirinternal structures for treatment, such as sensors and conductive wires,for example, may be placed in the lumen of the shaft 2. The distal sideof the conductive wire can be connected to an electrode provided on thesurface of the shaft 2, and the proximal side of the conductive wire canbe connected to a detector or power source through the proximal side ofthe catheter 1 so that electric signals from the electrode can bereceived or the electrode can be energized. The length in thelongitudinal direction d_(L), outer diameter, thickness etc. of theshaft 2 can be selected to be the appropriate size for the treatment.

The tip part 20 is preferably disposed at the distal end of the shaft 2.The tip part 20 may be a member different from or the same as the shaft2. When the tip part 20 is a member different from the shaft 2, the tippart 20 may be provided with a part that is inserted into the lumen ofthe shaft 2 or a part that projects distally from the distal end of theshaft 2. When the tip part 20 is a member integrated with the shaft 2,the distal end part of the shaft 2 may be formed by sealing the openingat the distal end of the shaft 2 by heat fusion or other means to formthe tip part 20.

The handle 7 is preferably disposed at the proximal side of the shaft 2,and the proximal end of the shaft 2 is preferably fixed to the inside ofthe handle 7. A conductive wire or a wire 30 described below extendingfrom the lumen of the shaft 2 is disposed within the handle 7. Tofacilitate manipulation of the wire 30, the handle 7 may include a wiremanipulator 70. By fixing the proximal end of the wire 30 to the wiremanipulator 70, the wire 30 can be pulled by operating the wiremanipulator 70 to bend the catheter distal part 2D of the catheter 1.

As shown in FIG. 2 to FIG. 7 , the catheter 1 has at least one wire 30having a distal end and a proximal end, the proximal end being disposedat a proximal end part of the shaft 2, and a distal end part of the wire30 being fixed to a distal end part of the shaft 2; and a leaf spring 40extending in the longitudinal direction d_(L) in the lumen of the shaft2 and having a distal end and a proximal end, a distal end part of theleaf spring 40 being fixed to the distal end part of the shaft 2 at asecond connection part 42. By pulling the wire 30, the shaft 2 can becurved. The leaf spring 40 can control the direction of the bending.

The wire 30 is an operating wire for manipulating the catheter distalpart 2D of the catheter 1 to bend. At least one wire 30 is provided, andfor example, two of the wire 30 may be provided to make the catheter 1capable of curving to both one side and the other side of the leafspring 40 in the radial direction d_(R), respectively, by operating eachwire 30. The wire 30 is disposed in the lumen of the shaft 2, and itsdistal end is fixed to the distal end part of the shaft 2, preferablythe tip part 20, and its proximal end is disposed at the proximal endpart of the handle 7. The proximal end part of the wire 30 is preferablyfixed to the handle 7. As the wire 30, metal wires such as stainlesssteel or wires formed from synthetic resins such as fluoroplastics canbe used. The wire 30 may be a single wire or may have a structureconsisting of multiple wires.

The leaf spring 40 is a member that defines the direction of curvatureof the catheter 1, and has a plate-like shape having a distal end andproximal end and extending in the longitudinal direction d_(L) of theshaft 2. The leaf spring 40 is preferably placed along the longitudinalaxis of the shaft 2. Since the leaf spring 40 has a plate-like shape,the direction of curvature of the catheter distal part 2D of thecatheter 1 can be defined, and the catheter distal part 2D can be curvedon one side or the other side in the radial direction d_(R). The distalend part of the leaf spring 40 is fixed to the distal end part of theshaft 2 at the second connection part 42. In the case where the tip part20 is provided at the distal end of the shaft 2, the distal end part ofthe leaf spring 40 is preferably fixed to the tip part 20. The proximalend part of the leaf spring 40 is fixed to a distal end part of the coil60 at a first connection part 41. In other words, the leaf spring 40 hasthe first connection part 41 where the proximal end part of the leafspring 40 is fixed to the distal end part of the coil 60 and the secondconnection part 42 where the distal end part of the leaf spring 40 isfixed to the distal end part of the shaft 2.

The leaf spring 40 is a spring using a plate material, and the materialsthat make up the leaf spring 40 includes metals such as stainless steel,titanium, carbon steel, nickel-titanium alloys, cobalt-chrome alloys,tungsten alloys. Alternatively, the materials that make up the leafspring 40 may include synthetic resin such as aromatic polyetherketoneresin (e.g., PEEK), polycarbonate resin, and fiber-reinforced resin.Alternatively, the leaf spring 40 may be made of natural rubber orsynthetic rubber such as butadiene rubber, isoprene rubber, styrenebutadiene rubber, ethylene propylene rubber, acrylic rubber, andsilicone rubber. Of these, the material of the leaf spring 40 ispreferably stainless steel.

The fixation of the distal end part of the wire 30 and the distal endpart of the leaf spring 40 to the shaft 2, or the first connection part41 of the proximal end part of the leaf spring 40 and the coil 60 may befixed by not fixing the ends directly, but by fixing the vicinity of theends. The method of fixing the distal end part or proximal end part ofthe wire 30 and the leaf spring 40 is not limited, and may include, forexample, solder, and when the tip part 20 and the coil 60 are metal,they are preferably fixed by laser welding.

As shown in FIG. 2 to FIG. 7 , a cover tube 50 and the coil 60 areplaced in the lumen of the catheter 1 from the distal side. The covertube 50 has a lumen extending in the longitudinal direction d_(L) inwhich the wire 30 and the leaf spring 40 are placed. The coil 60 has alumen extending in the longitudinal direction d_(L) and its distal endpart is fixed to the proximal end part of the leaf spring 40.

The cover tube 50 has a distal end, proximal end, and lumen extending inthe longitudinal direction d_(L) in the lumen of the shaft 2. As shownin FIG. 2 , the wire 30 and the leaf spring 40 are disposed in the lumenof the cover tube 50. The cover tube 50 is disposed outside the coil 60,and at least distal part of the coil 60 including the first connectionpart 41 where the leaf spring 40 and the coil 60 are fixed is placed inthe lumen of the cover tube 50. Placing at least distal part of the coil60 in the lumen of the cover tube 50 can prevent the distal part of thecoil 60 including the first connection part 41, which is the base of thebend when the catheter distal part 2D is curved by pulling the wire 30,from deforming, such as spreading in the radial direction d_(R), whichprevents the curving axis of the leaf spring 40 from twisting due torotation of the first connection part 41. As a result, the catheterdistal part 2D can be curved to a certain direction without twisting.

The cover tube 50 may cover the coil 60 in a section from the distal endto a certain position, or may cover the entire coil 60. From theviewpoint of reducing man-hours and costs in manufacturing, the proximalend of the cover tube 50 is preferably located in a section from thedistal end of the coil 60 to a certain proximal position. In this case,in the longitudinal direction d_(L) of the shaft 2, the length from theposition of the proximal end of the cover tube 50 to the distal end ofthe coil 60 is preferably ⅖ the length of the leaf spring 40 or longer.In other words, the coil 60 is preferably placed in the lumen of thecover tube 50 in the section having a length of ⅖ the length of the leafspring 40 or longer from the distal end of the coil 60. By making thecoil 60 covered by the cover tube 50 in the section having a length of ⅖or longer the length of the leaf spring 40, which is a curving member,from the distal end of the coil 60, the distal side of the coil 60 canbe sufficiently prevented from deforming such as spreading when thecatheter distal part 2D is curved by pulling the wire 30. While thelumen of the cover tube 50 houses the wire 30 and the leaf spring 40 ata position distal to the first connection part 41, the distal part ofthe cover tube 50 may be located at the distal end part of the shaft 2so that the wire 30 and the leaf spring 40 are not exposed from thecover tube 50, or the distal end of the cover tube 50 is located at aposition proximal to the distal end part of the shaft 2 so that the wire30 and the leaf spring 40 have a exposed part from the cover tube 50 atthe distal end part of the shaft 2.

The cover tube 50 preferably has flexibility, like the shaft 2, and thematerials that make up the cover tube 50 may include synthetic resinsuch as aromatic polyetherketone resin (e.g., PEEK), polycarbonateresin, polyamide-based resin, polyester-based resin, polyurethane-basedresin, polyolefin-based resin, vinyl chloride-based resin,silicone-based resin, natural rubber, and synthetic rubber. The covertube 50 is preferably formed by heat-shrinking such synthetic resins tothe outside of the coil 60.

As shown in FIG. 2 , the coil 60 has the distal end, proximal end, andlumen extending in the longitudinal direction d_(L) in the lumen of theshaft 2, and the wire 30 is disposed in the lumen. The coil 60 isdisposed at the proximal side of the leaf spring 40 in the lumen of theshaft 2, and has the first connection part 41 where the proximal endpart of the leaf spring 40 is fixed to the distal end part of the coil60. It is sufficient for the first connection part 41 to fix the leafspring 40 and the coil 60, and the proximal end of the leaf spring 40may be placed in the lumen of the coil 60 or may be placed outside thelumen of the coil 60. Alternatively, the proximal end of the leaf spring40 may be fixed to the distal end of the coil 60. At the firstconnection part 41, the coil 60 preferably receive the proximal end ofthe leaf spring 40 so that a part of the leaf spring 40 is placed in thelumen of the coil 60 to fix the proximal end part of the leaf spring 40.This allows for a stronger fixation between the leaf spring 40 and thecoil 60. As for the first connection part 41 where the leaf spring 40and the coil 60 are fixed, it can be said that the leaf spring 40 hasthe first connection part 41, or the coil 60 has the first connectionpart 41 as described above.

Providing the coil 60 can ensure stiffness at the base side of thecurvature of the catheter distal part 2D. From the viewpoint of securingstiffness of the base side of the curvature of the catheter distal part2D, the coil 60 is preferably a closely wound coil, that is, anuncompressed coil. The coil 60 that is uncompressed can make it easierfor the catheter distal part 2D to curve at the distal end of the coil60 as a starting point. Technically, an uncompressed coil has the ratioof a total length L_(c) at maximum compression to the total length L inits natural state L_(c)/L is 1. However, a coil with the ratio L_(c)/Lof 0.9 or more, 0.95 or more is substantially uncompressed, and includedin the uncompressed coil. The proximal end of the coil 60 may bepositioned at the proximal end of the shaft 2, or may be positioned inthe middle of the shaft 2. The coil 60 may switch to a different tube inthe middle of the shaft 2.

The coil 60 preferably has flexibility, and metals and resins can beused as the material, and the coil 60 can be made of metal wire such asstainless steel and nickel-titanium alloys and synthetic resin wire suchas aromatic polyetherketone resin (e.g., PEEK) and polycarbonate resin.The cross-sectional shape of the coil wire forming the coil 60 can becircular, quadrangular, or a combination thereof. Of these, the coil 60is preferably a coil made of stainless steel wire having a circularcross-sectional shape. The coil wire diameter, coil diameter, and lengthof the coil 60 can be appropriately selected as necessary. Inparticular, the coil 60 is preferably a coil wound with metal wire. Thediameter of coil wire forming the coil 60 is preferably 0.1 mm to 0.5mm. When the coil 60 is formed with coil wire having a quadrangularcross-sectional shape, one side of the quadrangle may be 0.05 mm to 1mm. Since the catheter 1 of the present invention has the internalstructure that switches at the distal end of the coil 60, the size,flexibility, and materials of the coil 60 is preferably selected so thatthe change in stiffness of the catheter 1 between the distal andproximal side with respect to the distal end of the coil 60 does notbecome significant.

The cover tube 50 has a first fixed part 51 fixed to the shaft 2 at aposition proximal to the distal end of the coil 60. By fixing the covertube 50, which encompasses the distal side of the coil 60 including thefirst connection part 41 where the leaf spring 40 and the coil 60 arefixed, to the shaft 2 at a position proximal to the distal end of thecoil 60, the coil 60 can be prevented from deforming, allowing thecatheter distal part 2D to bend in a certain direction while preventingthe shaft 2 from twisting. In addition, because the cover tube 50 havinga role as a restraining member for the coil 60 is fixed to the shaft 2instead fixing the coil 60 that has a certain stiffness and forms thebase part of curvature to the shaft 2, the shaft 2 is less likely tohave a stiffness step with a sudden change in hardness, and kinking anddecrease in pushability when the catheter distal part 2D is curved canbe prevented. Furthermore, because the coil 60 does not have a part thatexposes from the lumen of the cover tube 50 in the section from thedistal end of the coil 60 and the first fixed part 51 in thelongitudinal direction d_(L) of the shaft 2, problems such as twistingof the coil 60 in the section when the catheter distal part 2D is curvedby pulling the wire 30 can be prevented. The first fixed part 51 isformed by some fixing means, such as adhesion by glue and welding byresin, and the condition where the inner wall of the cover tube 50overlaps firmly the outer wall of the coil 60 when the cover tube 50 is,for example, formed on the outer side of the coil 60 by heat-shrinkingis not considered as the fixation.

As shown in FIG. 2 , FIG. 4 , and FIG. 5 , the first fixed part 51 ofthe cover tube 50 and the shaft 2 is provided between the outercircumference of the cover tube 50 and the inner circumference of theshaft 2, and has a length in the longitudinal direction d_(L) of thecover tube 50 and the shaft 2. The first fixed part 51 may be providedin all 360° of the circumference between the outer circumference of thecover tube 50 and the inner circumference of the shaft 2 as shown inFIG. 4 , or may be provided partially as shown in FIG. 5 . In the casewhere the first fixed part 51 is partially provided in a portion of the360° of the circumference as shown in FIG. 5 , the total angle at whichthe first fixed part 51 is present in the circumference is preferably60° or more, and more preferably 90° or more. When the lower limit ofthe total angle at which the first fixed part 51 is present in thecircumference is the above, the fixing strength can be ensured. Thetotal angle at which the first fixed part 51 is present in thecircumference may be 240° or less, or 180° or less. With the upper limitof the total angle at which the first fixed part 51 is present in thecircumference is the above, when the catheter 1 has a conductive wireconnected to an electrode or other device located at the distal end partof the catheter distal part 2D, the space formed between the outercircumference of the cover tube 50 and the inner circumference of theshaft 2 can provide a path for the conductive wire to be inserted. Insuch a configuration, the conductive wire is not fixed, which canprevent the conductive wire from being pulled when the catheter distalpart 2D is curved, enabling smooth bending operation.

The length of the first fixed part 51 in the longitudinal directiond_(L) is not particularly limited, and preferably a length of 50windings of the coil 60 or shorter, more preferably a length of 30windings or shorter, and even more preferably a length of 10 windings orshorter. Note that a length of one winding of the coil 60 is the lengthof the coil 60 in the axis direction that corresponds to the length ofone winding of the coil wire forming the coil 60. If the length of thefirst fixed part 51 in the longitudinal direction d_(L) is long, thestiffness of a portion of the shaft 2 where the first fixed part 51 isprovided becomes high, and the difference in stiffness may causeproblems such as kinking or reduced pushability. The length of the firstfixed part 51 in the longitudinal direction d_(L) shorter than or equalto the above can reduce the stiffness step of the shaft 2 due to thefirst fixed part 51, allowing the catheter distal end part 2D to becurved without problems such as kinking or reduced pushability. Inaddition, when the catheter 1 has a conductive wire connected to anelectrode or other device located at the distal end part of the catheterdistal part 2D, since the conductive wire is disposed inside the shaft 2and outside the cover tube 50, even if the first fixed part 51 isprovided at all circumference of the cover tube 50, the first fixed part51 having a short length in the longitudinal direction d_(L) canminimize the fixation of the conductive wire, preventing the conductivewire from being tugged and allowing smooth curving operation.

The catheter distal part 2D of the catheter 1 can be curved from aposition where the leaf spring 40 is exposed from the distal end of thecoil 60 to a position where the leaf spring 40 is fixed to the distalend part of the shaft 2, for example, the tip part 20. Accordingly, thelength of the curving portion of the catheter 1 can be appropriatelydetermined by the length of the leaf spring 40, the position of the tippart 20 and the first connection part 41.

It is preferred for the cover tube 50 to be in contact with the outsideof the coil 60. The cover tube 50 may be provided on the outside of thecoil 60 by heat-shrinking or other means to firmly overlap the outsideof the coil 60. The cover tube 50 being in contact with the outside ofthe coil 60 can prevent the coil 60 from deforming when the wire 30 isoperated. It is not necessary for the cover tube 50 to be in contactwith the outside of the coil 60 in all of the portion that encompassesthe coil 60, and the portion from the distal end of the coil 60 to aslightly proximal position, for example, a portion having a length of 3windings of the coil 60 or shorter may not be in contact with the covertube 50. The definition of the length of the windings of the coil 60 isthe same as described above. Thus, even if the cover tube 50 has aportion that is not in contact with the outside of the coil 60, thecover tube 50 is in contact with the coil 60 in most of the areas thatencompasses the coil 60 and can prevent the coil 60 from deforming.

As shown in FIG. 2 , the length d from the distal end of the first fixedpart 51 to the distal end of the coil 60 is preferably 2 times thelength of the leaf spring 40 or shorter in the longitudinal directiond_(L). If the length d from the distal end of the first fixed part 51 tothe distal end of the coil 60 is longer than the above range, the leafspring 40 and the coil 60 may become twisted due to friction and thelike with the inner layer of the shaft 2 when the entire shaft 2 istwisted, and the cover tube 50 in such a condition encompassing the coil60 may be fixed to the shaft 2. Then, even if the twisted shaft 2 isrecovered to an untwisted state, the leaf spring 40 may remain twisted,and the catheter distal part 2D may not be able to bend in a certaindirection and instead may curve spirally, resulting in that the catheterdistal part 2D cannot be delivered to the desired position. When thelength from the distal end of the first fixed part 51 to the distal endof the coil 60 is 2 times or shorter the length of the leaf spring 40,which is a curving member, as described above, the cover tube 50 in anuntwisted state encompassing the leaf spring 40 and the coil 60 can befixed to the shaft 2, allowing the catheter distal part 2D to be curvedto a certain direction without twisting. In the longitudinal directiond_(L) of the shaft 2, the proximal end of the first fixed part 51 andthe proximal end of the cover tube 50 may be located at the sameposition. The length d from the distal end of the first fixed part 51and the distal end of the coil 60 in the longitudinal direction d_(L) ofthe shaft 2 is more preferably 1.5 times the length of the leaf spring40 or shorter, and even more preferably 1 time or shorter.

The length d from the distal end of the first fixed part 51 to thedistal end of the coil 60 is preferably ⅓ the length of the leaf spring40 or longer in the longitudinal direction d_(L). The catheter distalpart 2D is stiffer in the section in the longitudinal direction d_(L)where the coil 60 is present due to the stiffness of the coil 60 itself,and less stiff in the section where the coil 60 is not present. Inaddition, since the first connection part 41 where the leaf spring 40 isfixed to the distal end part of the coil 60 is also a part that hasincreased stiffness, some change in stiffness is inevitable at thedistal end of the coil 60. At the same time, since the stiffness is alsoincreased at the first fixed part 51, the first fixed part 51 is also acause of stiffness steps. However, when the catheter 1 is configured sothat the length from the distal end of the first fixed part 51 to thedistal end of the coil 60 is longer than or equal to the abovepredetermined value with respect to the length of the leaf spring 40,which is a curving member, since the stiffness change at the distal endof the coil 60 and the stiffness change due to the first fixed part 51do not overlap, the stiffness change can be distributed, resulting inthe prevention of sudden stiffness step in the shaft 2, which canprevent or reduce kinking and reduced pushability when the catheterdistal part 2D is curved. The length d from the distal end of the firstfixed part 51 to the distal end of the coil 60 in the longitudinaldirection d_(L) of the shaft 2 may be ½ the length of the leaf spring 40or longer, or may be ¾ or longer.

The first fixed part 51 is preferably located proximal to the firstconnection part 41 where the leaf spring 40 is fixed to the coil 60. Asshown in FIG. 2 , while the coil 60 has the first connection part 41where the proximal end part of the leaf spring 40 is fixed to the distalend part of the coil 60, the first connection part 41 does notnecessarily have to be located at the distal end of the coil 60, andalthough not shown in the figures, it is also acceptable for the firstconnection part 41 to be located at a position somewhat proximal to thedistal end of the coil 60. Even in such a case, the first fixed part 51is preferably located proximal to the first connection part 41. When thecatheter distal part 2D is curved by pulling the wire 30, a part of thecoil 60 located proximal to the first connection part 41 may deform suchas spreading, causing the first connection part 41 to twist, resultingin that the leaf spring 40 is twisted and the catheter distal part 2Dcannot be curved to a certain direction. However, by providing the firstfixed part 51 at a position proximal to the first connection part 41, apart of the coil 60 located proximal to the first connection part 41 canbe prevented from deforming.

Preferably, the cover tube 50 is not fixed to the shaft 2 in the sectionfrom the distal end of the first fixed part 51 to the distal end of thecoil 60 in the longitudinal direction d_(L) of the shaft 2. This resultsin that no part from the distal end of the first fixed part 51 to thedistal end of the coil 60 becomes stiffer due to fixation, stiffnesssteps in the shaft 2 can be prevented to prevent kinking of the catheterdistal part 2D and reduced pushability. In addition, when the catheter 1has a conductive wire connected to an electrode or other device disposedat the distal end part of the catheter distal part 2D, the absence of afixed part between the distal end of the first fixed part 51 and thedistal end of the coil 60 prevents problems such as the conductive wirebeing tugged when the catheter distal part 2D is curved by pulling thewire 30.

Although not shown in the figures, the cover tube 50 may be fixed to theshaft 2 at a position proximal to the proximal end of the first fixedpart 51 in the longitudinal direction d_(L), and there may be more thanone of these fixed parts. Although an additional fixed part disposed ata position proximal to the proximal end of the first fixed part 51 hasless effect on change in stiffness because it is apart from the distalend of the coil 60 and the first connection part 41, from a viewpoint ofreduction in man hours and sliding property of the conductive wire whenthe catheter 1 has a conductive wire, it is preferable for theadditional fixed part that is provided at a position proximal to theproximal end side of the first fixed part 51 to be minimum.

As shown in FIG. 8 , the first fixed part 51 fixes the shaft 2 and thecover tube 50, and may also fix the shaft 2, the cover tube 50, and thecoil 60. The fixation of the shaft 2, the cover tube 50, and the coil 60means that the shaft 2, the cover tube 50, and the coil 60 are directlyfixed by some fixing means, such as adhesion by glue, welding by resin,brazing by solder, etc. As shown in FIG. 8 , the portion where the shaft2 and the cover tube 50 are fixed and the portion where the shaft 2 andthe coil 60 are fixed may be formed continuously as the first fixed part51, or although not shown in the figures, the shaft 2 and the cover tube50 are fixed by fixing means, and the cover tube 50 and the coil 60 arefixed by fixing means, and thereby, the first fixed part 51 may beformed. In this way, the coil 60 is further fixed to the cover tube 50and the shaft 2 at the first fixed part 51, which can prevent the coil60 from deforming due to the first fixed part 51 and increase the effectof preventing the shaft 2 from twisting.

As shown FIG. 9 , the catheter 1 may further have a second fixed part 61where the shaft 2 and the coil 60 are fixed at a position proximal tothe first fixed part 51 in the longitudinal direction d_(L) of the shaft2. By providing the second fixed part 61 where the coil 60 and the shaft2 are fixed at a position proximal to the first fixed part 51 where thecover tube 50 and the shaft 2 are fixed, the effect of preventing thecoil 60 from twisting can be improved while preventing stiffness stepsof the catheter distal part 2D.

The length of the cover tube 50 in the longitudinal direction d_(L) ispreferably longer than the length of the leaf spring 40 in thelongitudinal direction d_(L). The cover tube 50 having a longer lengthin the longitudinal direction d_(L) than the length of the leaf spring40 in the longitudinal direction d_(L) can encase the leaf spring 40 andthe wire 30 at the side distal to the first connection part 41 in thelongitudinal direction in its lumen while encasing the distal side ofthe coil 60 including the first connection part 41, which can preventthe coil 60 from deforming and allow the leaf spring 40 and the wire 30to be protected.

As shown in FIG. 10 , the cover tube 50 preferably extends to the secondconnection part 42 where the distal end part of the leaf spring 40 isfixed to the shaft 2, and the cover tube 50 preferably covers the wire30 and the leaf spring 40 so that the leaf spring 40 and the wire 30 arenot exposed in the lumen of the shaft 2. Such a configuration canprotect the leaf spring 40 and the wire 30, which repeatedly move in acurved motion by the bending operation at the bendable catheter distalpart 2D. In addition, when the catheter 1 has a conductive wireconnected to an electrode or other device disposed at the distal endpart of the catheter distal part 2D, the conductive wire is placedinside the shaft 2 and outside the cover tube 50. On the other hand, theleaf spring 40 and the wire 30 are not exposed outside the cover tube 50and in the lumen of the shaft 2 since the leaf spring 40 and the wire 30are placed in the lumen of the cover tube 50, and therefore,interference of the leaf spring 40 and the wire 30 with the conductivewire can be prevented. The embodiments in which the cover tube 50extends to the second connection part 42 includes an embodiment wherethe cover tube 50 extends to the proximal end of the second connectionpart 42 and an embodiment where the cover tube 50 extends to thevicinity of the proximal end of the second connection part 42.

The present invention claims priority based on Japanese PatentApplication No. 2020-117632 filed on Jul. 8, 2020. All the contentsdescribed in Japanese Patent Application No. 2020-117632 filed on Jul.8, 2020 are incorporated herein by reference.

DESCRIPTION OF REFERENCE SIGNS

-   -   1: catheter    -   2: shaft    -   2D: catheter distal part    -   7: handle    -   20: tip part    -   30: wire    -   40: leaf spring    -   41: first connection part    -   42: second connection part    -   50: cover tube    -   51: first fixed part    -   60: coil    -   61: second fixed part    -   70: wire manipulator    -   d: length from the distal end of the first fixed part to the        distal end of the coil    -   d_(L): longitudinal direction    -   d_(R): radial direction

1. An electrode catheter, comprising: a shaft having a distal end, aproximal end, and a lumen extending in a longitudinal direction; atleast one wire having a distal end and a proximal end, the proximal endbeing disposed at a proximal end part of the shaft, and a distal endpart of the wire being fixed to a distal end part of the shaft; a coilhaving a distal end, a proximal end, and a lumen in which the wire isdisposed and extending in the longitudinal direction in the lumen of theshaft; a leaf spring having a distal end and a proximal end andextending in the longitudinal direction in the lumen of the shaft; acover tube having a distal end, a proximal end, and a lumen extending inthe longitudinal direction in the lumen of the shaft; an electrodedisposed on a surface of the shaft; a conductive wire connected to theelectrode and disposed inside the shaft and outside the cover tube, anda first fixed part where the cover tube is fixed to the shaft at aposition proximal to the distal end of the coil in the longitudinaldirection, wherein the leaf spring has a first connection part where aproximal end part of the leaf spring is fixed to a distal end part ofthe coil, and a second connection part where a distal end part of theleaf spring is fixed to a distal end part of the shaft; the wire, theleaf spring, and the first connection part are disposed in the lumen ofthe cover tube; and the cover tube is disposed outside the coil.
 2. Theelectrode catheter according to claim 1, wherein a part of an innersurface of the cover tube is in contact with the outside of the coil. 3.The electrode catheter according to claim 1, wherein a length from adistal end of the first fixed part to the distal end of the coil is 2times a length of the leaf spring or shorter in the longitudinaldirection.
 4. The electrode catheter according to claim 1, wherein alength from a distal end of the first fixed part to the distal end ofthe coil is ⅓ a length of the leaf spring or longer in the longitudinaldirection.
 5. The electrode catheter according to claim 1, wherein thefirst fixed part is located proximal to the first connection part. 6.The electrode catheter according to claim 1, wherein the cover tube isnot fixed to the shaft in the section from a distal end of the firstfixed part to the distal end of the coil in the longitudinal direction.7. The electrode catheter according to claim 1, wherein the shaft, thecover tube, and the coil are fixed at the first fixed part.
 8. Theelectrode catheter according to claim 1, further comprising a secondfixed part where the shaft and the coil are fixed at a position proximalto the first fixed part in the longitudinal direction.
 9. The electrodecatheter according to claim 1, wherein a longitudinal length of thecover tube is longer than a longitudinal length of the leaf spring. 10.The electrode catheter according to claim 1, wherein the cover tubeextends to the second connection part, and the cover tube covers thewire and the leaf spring so that the wire and the leaf spring are notexposed in the lumen of the shaft.